Related Experiment Videos
Enhanced ribosomal association of p27(Kip1) mRNA is a mechanism contributing to accumulation during growth arrest
S S Millard1, J S Yan, H Nguyen
1Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Abstract:
p27(Kip1) regulates the decision to enter into S-phase or withdraw from the cell cycle by establishing an inhibitory threshold above which G1 cyclin-dependent kinases accumulate before activation. We have used the HL-60 cell line to study regulation of p27 as cells withdraw from the cell cycle following treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA). We found that the amount of p27 is maximal in G0 cells, lower in G1 cells, and undetectable in S-phase cells. In contrast to the protein, the amount of p27 mRNA was the same in these populations, suggesting that accumulation of p27 during the cell cycle and as cells withdraw from the cell cycle is controlled by post-transcriptional mechanisms. In S-phase cells, the degradation of p27 appears to predominate as a regulatory mechanism. In G0 cells, there was an increase in the synthesis rate of p27. Our data demonstrate that, in G0 cells, accumulation of p27 is due to an increase in the amount of p27 mRNA in polyribosomes.
Insights
The cell cycle regulator p27(Kip1) is controlled post-transcriptionally. Its accumulation in G0 cells involves increased p27 mRNA in polyribosomes, while degradation dominates in S-phase cells.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- p27(Kip1) is a key regulator of cell cycle progression, particularly the transition from G1 to S-phase.
- Dysregulation of p27(Kip1) is implicated in various cancers.
- Understanding p27(Kip1) regulation is crucial for cell cycle control research.
Purpose of the Study:
- To investigate the post-transcriptional regulation of p27(Kip1) during cell cycle withdrawal.
- To elucidate the mechanisms controlling p27(Kip1) levels in G0 and S-phase cells.
- To analyze the role of mRNA and protein synthesis/degradation in p27(Kip1) regulation.
Main Methods:
- Utilized the HL-60 cell line treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) to induce cell cycle withdrawal.
- Quantified p27(Kip1) protein and mRNA levels in different cell cycle phases (G0, G1, S).
- Assessed p27(Kip1) synthesis rates and degradation mechanisms.
- Analyzed p27(Kip1) mRNA association with polyribosomes.
Main Results:
- p27(Kip1) protein levels were maximal in G0, lower in G1, and undetectable in S-phase.
- p27(Kip1) mRNA levels remained constant across cell cycle phases, indicating post-transcriptional control.
- Protein degradation was the primary regulatory mechanism in S-phase cells.
- Increased p27(Kip1) synthesis and elevated p27(Kip1) mRNA in polyribosomes were observed in G0 cells.
Conclusions:
- p27(Kip1) accumulation during cell cycle withdrawal is primarily regulated by post-transcriptional mechanisms.
- In G0 cells, increased p27(Kip1) levels are achieved through enhanced mRNA translation.
- Degradation plays a significant role in reducing p27(Kip1) levels during S-phase entry.